Density of states and zero Landau Level probed through capacitance of graphene

We report capacitors in which a finite electronic compressibility of graphene dominates the electrostatics, resulting in pronounced changes in capacitance as a function of magnetic field and carrier concentration. The capacitance measurements have allowed us to accurately map the density of states D, and compare it against theoretical predictions. Landau oscillations in D are robust and zero Landau level (LL) can easily be seen at room temperature in moderate fields. The broadening of LLs is strongly affected by charge inhomogeneity that leads to zero LL being broader than other levels.     

Fragmentation production of charmed hadrons in electron-positron annihilation

Processes involving the production of D* mesons and Λ _c baryons in electron-positron annihilation at the energies of 10.58 and 91.18 GeV are considered. At the energy of 10.58 GeV, the production of pairs of B mesons that is followed by their decay to charmed particles is analyzed along with direct charm production. The violation of scaling in the respective fragmentation functions is taken into account in the next-to-leading-logarithmic approximation of perturbative QCD. The required nonperturbative fragmentation functions are extracted numerically from experimental data obtained at B factories and are approximated by simple analytic expressions. It is shown that the difference in the nonperturbative fragmentation functions for transitions to mesons and baryons can readily be explained on the basis of the quark-counting rules.     

On segregation manifestations of the long-range effect during the ion implantation of rolled copper-nickel foils

Segregation manifestations of the long-range effect during the irradiation of rolled nonequilibrium Cu₈₀Ni₂₀ alloy foils with B⁺ ions are studied. The composition separation of Cu and Ni in the surface layers of the unirradiated side of the foil is revealed. This separation leads to the formation of the nonmonotonic concentration profiles of Ni and Cu. A phenomenological model for the formation of the chemical composition of the surface layers on the unirradiated side of the foil is proposed. It is based on the assumption of the simultaneous effects of the generation of elastic waves and changes in local mechanical stresses.     

Nitrogen oxide conversion in nitrogen-oxygen mixtures excited by a microsecond electron beam

The removal of nitrogen oxides from gas mixtures under the action of an ionizing microsecond pulsed electron beam is studied experimentally. Experiments were carried out with gas mixtures simulating flue gases of thermal power plants. The current density and pulse duration of the electron beam, as well as the concentrations of oxygen and the impurity to be removed, are shown to affect the cleaning characteristics. It is found that the nitrogen oxide conversion initiated by a pulsed electron beam cannot be described by models developed for steady-state electron beams.     

Effect of Temperature on the Yields of Final Products in the γ-Radiolysis of Formaldehyde Solutions in C1–C3 Alkanols

The effect of temperature on the yields of 1,2-alkanediols in the -radiolysis of the methanol(or ethanol)–formaldehyde (0.9 M) systems and on the yields of 1,2-alkanediols, carbonyl compounds, methanol, and ethanol in the -radiolysis of the 1-propanol(or 2-propanol)–formaldehyde (1 M) systems was studied over the range 373–473 K. It was found that the temperature dependence of the yields of 1,2-butanediol and 2-methyl-1,2-propanediol exhibited maximums at 423 and 373 K, respectively.     

Ionic liquids and their use for the dissolution of natural polymers

The experimental and calculated data on the structure and properties of ionic liquids are presented. The prospects for their use as the solvents for natural polymers are considered.     

Fast 5d → 4f luminescence of Pr in Lu2SiO5 single crystal host

Absorption and photoluminescence spectra including the decay kinetics of the Pr³⁺-doped Lu₂SiO₅ were measured. Fast luminescence originating from the radiative 5d → 4f transition of Pr³⁺ center is revealed with the maximum at 273 nm at room temperature. Low temperature photoluminescence decay is governed by the 25 ns decay, while substantial shortening to 6–7 ns occurs at room temperature. With the help of slow decay measurement in the millisecond time scale we evidence the thermal ionization of the relaxed excited 5d₁ state of Pr³⁺. The ionization can explain the observed temperature dependences of the decay times and emission intensity.     

Silver nanoparticles on fibers and films of <Emphasis Type="Italic">Bombyx mori</Emphasis> silk fibroin

Possibility of obtaining silver nanoparticles on fibers and films of silk fibroin was studied. A comparative assessment of the effect of reducing agents on the morphology and size of silver particles on the fiber surface was made.     

Base Hydrolysis and Use of Cationic Ammonium Dyes in Which the Chromophore System Is not Conjugated with the Nitrogen Atom

The capability of cationic dyes in which the onium group is not conjugated with the chromophore system to form aqueous dispersions in a weakly alkaline medium was examined. Such dyes can be fixed on a fiber in increased amounts owing to their binding not only in the cationic form but also in the hydrolyzed monomolecular form.     

Thermodynamics and kinetics of initial gas phase reactions in chemical vapor deposition of titanium nitride. Theoretical study of TiCl4 ammonolysis

Thermodynamic equilibrium and kinetics of the gas‐phase reaction between TiCl₄ and NH₃ have been studied computationally using results from recent quantum mechanical calculations of titanium tetrachloride ammonolysis. 1 These calculations were based upon the transition state theory for the direct reactions and RRKM theory for the reactions proceeding via intermediate complex. Rate constants for the barrierless reactions were expressed through the thermodynamic characteristics of the reagents and products using a semiempirical variational method. The kinetic simulation of the gas‐phase steps of CVD was performed within a model of a well‐stirred reactor at temperatures 300–1200 K and residence times between 0.1–2 s. At temperatures below 450 K formation of donor–acceptor complexes between TiCl₄ and NH₃ is the dominating process. At higher temperatures sequential direct ammonolysis takes place. At typical LPCVD conditions the only product of the first step of ammonolysis, TiCl₃NH₂, is formed in substantial amount. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1366–1376, 2001